Preheat your oven to 400°F (200°C). Line a standard 12-cup muffin tin with paper liners or grease it thoroughly.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, light brown sugar, baking soda, and salt until well combined. Set aside.

In a separate medium mixing bowl, mash the ripe bananas with a fork or potato masher until mostly smooth with a few small lumps remaining. Add the large egg, vegetable oil (or melted butter), milk, and vanilla extract to the mashed bananas. Whisk until thoroughly combined.

Pour the wet ingredient mixture into the dry ingredient mixture. With a rubber spatula, gently fold until just combined. Be careful not to overmix; a few lumps are perfectly fine. Overmixing will result in tough muffins.

Gently fold in the semi-sweet chocolate chips until evenly distributed throughout the batter.

Divide the batter evenly among the 12 prepared muffin cups, filling each about two-thirds full. If desired, sprinkle a few extra chocolate chips on top of each muffin for an appealing finish.

Bake at 400°F (200°C) for 5 minutes. Then, without opening the oven door, reduce the oven temperature to 375°F (190°C) and continue baking for another 13-15 minutes, or until a wooden skewer inserted into the center of a muffin comes out clean or with moist crumbs attached (no wet batter).

Once baked, remove the muffin tin from the oven and let the muffins cool in the tin for 5 minutes. This helps them set up and prevents sticking.

Carefully transfer the muffins to a wire rack to cool completely. These muffins are best enjoyed warm or at room temperature.